1. Field of the Invention
The present invention relates to a functional film, and a method for producing the functional film. More specifically, the present invention relates to a functional film having a laminated structure, which is provided by feeding a substrate having a coating film formed thereon from a film roll obtained by winding up the substrate and forming an inorganic film on the coating film, and to a method for producing the functional film.
2. Description of the Related Art
Functional films such as gas barrier films, protective films, optical filters, and anti-reflection films are used in a variety of devices, for example, optical elements, display devices such as liquid crystal display and organic EL display; semiconductor devices; and thin-film solar cells.
Meanwhile, for producing these functional films, film formation techniques through vacuum film forming methods such as sputtering, and plasma CVD method are used. In order to efficiently form a film while ensuring high productivity, it is carried out to continuously form a film on a lengthy base material.
One method for producing the above-mentioned functional film in described below. A lengthy substrate is continuously fed from a film roll. Then, a coating liquid is coated on the substrate, dried and cured to form a coating film, and the substrate having the coating film formed thereon is wound up to thereby produce a film roll. Next, the film roll having the coating film formed thereon is placed in a feeding section of a vacuum film-forming apparatus, and the substrate is continuously fed from the film roll to a film formation chamber. Then, in the film formation chamber, an inorganic film is formed on the coating film to form a film having a laminated structure composed of the coating film and the inorganic film, and the film having a laminated structure is wound up, thereby producing a film roll. As equipment for carrying out such a film forming method, there has been known a so-called roll-to-roll film-forming apparatus. By repeating the process for forming a coating film and an inorganic film at plural times by the film-forming apparatus, it is possible to produce a functional film having a plurality of laminated structures.
In the above production method, in order to prevent winding misalignments during film formation of an inorganic film and to maintain uniform quality of a resulting functional film, Japanese Patent Application Laid-Open No. 08-92727 describes a method in which a film roll wound with a winding hardness of 70 to 95 is placed in a feeding section of a vacuum film-forming apparatus, and an inorganic film is continuously formed on a substrate.
Further, Japanese Patent Application Laid-Open No. 06-60374 describes a method in which a wound roll of a lengthy plastic film is introduced into a vapor deposition chamber, the inside of the vapor deposition chamber is depressurized to a pressure of 20 Torr over 2 minutes or more, and subsequently the inside of the chamber is vacuum evacuated to a usual vapor deposition pressure, thereby making a ferromagnetic alloy or an alloy adhere on the plastic film by a vapor deposition method.